Telephone headset



Dec. 9 1,521,275

a. w. CARPENTER ET AL TELEPHONE HEADSET Original Fi1ed Jan. 29, 19216R0: nu,

Patented Dec. 30,1924.

UNITED STATES PATENT FFIC GLENN W- CARPENTER AND WENDELL L. CARLSON, FSCHENECTADY, NEW YORK.

TELEPHONE HEADSET.

Original application filed January 29, 1921, Serial No. 440,982. Dividedand this application filed April 25, 1924. Serial No. 709,050.

To all whom, it may concern:

Be it known that we, GLENN W. CARPEN- Ten and 'WENDELL L. CARLsoN,citizens of the United States, residing at Schenectady,

in the county of Schenectady and State of New York, have inventedcertain new-and useful Improvements in Telephone Headsets, of which thefollowing is a specification. I Our-invention relates broadly toelectromagnetic telephone receivers and more particularly to telephoneheadsets for use in radio receiver circuits, and has for an object toprevent the deleterious efi'ects caused by ,15 electrostatic,electromagnetic and direct coupling which normally exists between thetelephone receiver circuit and other circuits particularly with circuitsin multistagepr igh power radio receiving electron tube amplifiers ofgreat sensitivity.

This application is a division of our application Serial Number 440,992filed J anuary 29, 1921.

Another object of our invention is to shield the telephone cords of theheadset from strays or any external electrical disturbances whichnormally tend to afi'ect a sensitive electron tube amplifier.

Still another object of the invention is to provide a construction offlexible electri-- cally' shielded cord for telephone headsets wherein ashield or braiding of tinsel thread is woven. over'the conductorsthroughout their length and which may be connected at one end with a lowpqtential circuit and at the other end with the telephone receivercasings. v

'Great difliculty has been encountered heretofore whentelephone'receivers were used in conjunction with high amplificationelectron tube apparatus, due to the fact that a coupling exists betweenthe telephone receiver circuit and other circuits in t e apparatus orexternal circuits. This coupling, insome instances, causes a detuning ofthe oscillatory circuit, while in other cases it produces oscillationsin the tele hone receiver circuit which is commonly own as howling whenof an audio frequency. J 4 I i We will now describe in detail ourshielded telephone head set which prevents the above described coupling,references be which Figure 1 is a perspective view of the telephonereceivers and connecting cords, parts being broken away to more clearlyshow the construction; Figure 2 is a detail perspective vlew of aportion of the telephonecord, showing an embodiment of the invention inthe construction of the cords and arrangement of the conductors therein;and Figure 3 shows a modified construction of the flexible electricalshield surrounding the telephone conductors in accordance with ourinvention. I j

Our invention contemplates the provision of an extremely flexiblemetallic tinsel braid woven over the telephone cords on the headset. Thetinsel braid may be formed from fine copper wires each of which has atextile core in the wellknown manner of standard stranded electricalconductors, the several textile cores and wound wires bein braided toform a substantially closed flexi le housing throughout the length ofthe cords. The ends of the shield may also serve as a stay cord toprevent any undue strain being placed upon the conductor itself.

Referring more particularly to the drawings, Fig. 1 is a perspectiveview of our im-' proved telephone headset in which reference characters22 designate the insulated conductors which lead to the telephonereceivers 3- 3. These conductors may be covered with the usualinsulating cotton cord covering 7 "if desired. Surrounding the insulatedconductors and the cotton covering, if thelatter is used, is a flexiblemetallic casin or shield 4. {[he shield 4 is constructed 0 woven tinselconductors as more fully shown in Figs. 2 and 3, that is to say,flexible metallic conductors braided together. As illustrated in thedrawin s, the metallic strands of the shield 4-may e substantially thesame as the metallicstrandsof conductors 2- -2 and may be helicallywound with a. textile core the same manner as the strands of conductors2-2 are ordinarily twisted. This flexible casing or shield is directlyconnected to the telephone receiver casings and headband as indicated at5-5. The tinsel braiding may be more closely-woven at the points 5-5where the conductors are brought out of the braiding to provide aconducting strand which may be grounded to the casings of the telephonereceivers and which mayalso serve as a stay cord to prevent any unduestrain being placed upon the conductor itself. That portion of theshield indicated by reference character 6 may also be more closely woventhan the other part of the shield to provide a connection to a' lowpotential circuit or ground at the same time that it serves as a tiecord for thetelephone conductors. Reference character 8 indicates aninsulated protective covering or braiding which is placed over theflexible metallic shield.

In Fig. 3 we have represented a modified form of flexible electricalshield for telephone headsets wherein one of the conductOIs is arrangedwithin the other, the outer conductor being hollow to receive the'innerconductor. That is to say, the shield indicated by reference character 4in Fig. 3 surrounds but is insulated from an inner conductor 2, theshield 4 serving as one of the conductors.

When a metallic shield is not used with telephone headsets in connectionwith sensitive electron tube amplifiers, any alternating currentenergyexisting in the telephone receiver circuit may by electrostatic orelectromagnetic coupling, existing between the conductors and othercircuits in the apparatus, cause oscillations to be set up in theamplifier circuits. If these conductors are now enclosed in a metallicshield, which shield is preferably electrically connected with thetelephone shells and with a low potential conductor, it is apparent thatthe shield will prevent the couplings referred to and there fore preventan effective transfer of energy from the circuit formed by the telephoneconductors, thus eliminating this well-known annoying disturbance.

Our invention finds application in all multistage electron tube circuitsconnected to actuate a responsive device in which the usual reactionmust be eliminated employed in connection with either line wire carrierwave systems or in radio systems. By use of the invention manyadditional stages of amplification may be employed and arranged tofunction without the inherent reaction of circuits which would occurunder normal circumstances.

hat we claim and desire to secure by Letters Patent of the United Statesis as follows:

1. A telephone headset, comprising in combination a pair ofelectromagnetic sound reproducing devices, an insulated conductorconnecting said devices, a flexible braided shield surrounding saidconductor, said shield consisting of woven tinsel conductors and aprotecting braid about said shield.

2. A telephone headset, comprising in combination a pair ofelectromagnetic sound reproducing devices, an insulated conductorconnecting said devices, a flexible braided shield surrounding saidconductor, said shield consisting of closely woven metallic conductorsterminating in stay cords at each end 'for preventing any undue strainbeing placed upon said insulated conductors.

3. A telephone headset, comprising in combination a pair ofelectromagnetic sound. reproducing devices, an insulated conductorconnecting said devices, a flexible braided shield surrounding saidconductor, said shield continuing beyond the ends of said insulatedconductor to provide stay cords atthe telephone receiver ends of saidinsulated conductor, and a tie cord formed by said shield at theopposite end of said insulated conductor opposite said telephonereceiver end.

4. A receiver cord comprisin a plurality of insulated conductors, aexible electrical metallic shield surrounding said insulated conductorssaid shield continuing beyond the ends of said conductors to providestay cords, and a textile protective braiding about said shield.

5. A telephone headset, comprising in combination a pair ofelectromagnetic sound reproducing devices, an insulated conductorconnecting said devices, an electrostatic shield completely surroundingsaid insulated conductor, said shield comprising a plurality of flexiblebraided tinsel con uctors and serving" as a connection separate fromsaid first mentioned connection between said devices. v

GLENN CARPENTER. WENDELL L. CARLSON.

